“I was greatly disturbed to read this weekend’s article in the Connecticut Post describing the report of 7,100 defects that the FRA has discovered on the Metro-North railroad system,” Blumenthal wrote in a letter to Joseph C. Szabo, administrator of the agency.

“This report, along with my own analysis ... leads to serious questions about the adequacy of scrutiny and oversight by federal agencies responsible for assuring safety and reliability,” he said.

Only after a Dec. 1 Metro-North derailment near the Spuyten Duyvil station in the Bronx killed four passengers and injured 59, did the FRA initiate a thorough investigation of the railroad.

“I am absolutely determined to leave no stone unturned in seeking explanations for this powerful information from the federal agency and the railroad,” Blumenthal said Monday.